U.S. patent application number 11/969955 was filed with the patent office on 2008-07-24 for battery unit.
This patent application is currently assigned to NISSAN MOTOR CO., LTD.. Invention is credited to Susumu KOMIYAMA, Yuki KOSAKA, Kazuhiro TAKEDA.
Application Number | 20080174274 11/969955 |
Document ID | / |
Family ID | 39640592 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080174274 |
Kind Code |
A1 |
KOSAKA; Yuki ; et
al. |
July 24, 2008 |
BATTERY UNIT
Abstract
A battery unit has positive and negative terminals, a pair of
battery modules, three switch modules, a bypass line and a
controller. A first battery module is connected to the positive and
negative terminals. The second battery module is connected in
parallel with the first battery module. Each battery module
includes a battery and a reactor connected together in series. The
first switch module extends between the negative terminal and a
negative electrode side of the first battery module. The second
switch module extends between positive electrode sides of the first
and second battery modules. The bypass line connects a point lying
between the first battery module and the first switch module to a
point lying between the second battery module and the second switch
module. The third switch module is arranged in the bypass line. The
controller controls an on-off state of each of the switch
modules.
Inventors: |
KOSAKA; Yuki; (Yokohama-shi,
JP) ; KOMIYAMA; Susumu; ( Tokyo, JP) ; TAKEDA;
Kazuhiro; (Yokosuka-shi, JP) |
Correspondence
Address: |
GLOBAL IP COUNSELORS, LLP
1233 20TH STREET, NW, SUITE 700
WASHINGTON
DC
20036-2680
US
|
Assignee: |
NISSAN MOTOR CO., LTD.
Yokohama
JP
|
Family ID: |
39640592 |
Appl. No.: |
11/969955 |
Filed: |
January 7, 2008 |
Current U.S.
Class: |
320/117 |
Current CPC
Class: |
H02J 7/0016 20130101;
Y02T 10/70 20130101; Y02T 10/7005 20130101; H02J 7/1423 20130101;
Y02T 10/7055 20130101 |
Class at
Publication: |
320/117 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2007 |
JP |
2007-009357 |
Claims
1. A battery unit comprising: a positive electrode terminal; a
negative electrode terminal; a first battery module connected to
the positive and negative electrode terminals, and including a
first battery and a first reactor connected together in series; a
second battery module connected in parallel with the first battery
module, and including a second battery and a second reactor
connected together in series; a first switch module arranged
between the negative electrode terminal and a negative electrode
side of the first battery module; a second switch module arranged
between a positive electrode side of the first battery module and a
positive electrode side of the second battery module; a bypass line
connecting a point lying between the first battery module and the
first switch module to a point lying between the second battery
module and the second switch module; a third switch module arranged
in the bypass line; and a controller operatively arranged to
selectively control an on-off state of each of the first, second
and third switch modules.
2. The battery unit as recited in claim 1, wherein the first switch
module includes a first diode arranged to allow a flow of electric
current from the negative electrode terminal to the negative
electrode side of the first battery module, and a first switch
arranged to selectively connect and disconnect a flow of electric
current from the negative electrode side of the first battery
module to the negative electrode terminal; the second switch module
includes a second diode arranged to allow a flow of electric
current from the positive electrode side of the second battery
module to the positive electrode side of the first battery module,
and a second switch arranged to selectively connect and disconnect
a flow of electric current from the positive electrode side of the
first battery module to the positive electrode side of the second
battery module; and the third switch module includes a third diode
arranged to allow a flow of electric current from the negative
electrode side of the first battery module to the positive
electrode side of the second battery module, and a third switch
arranged to selectively connect and disconnect a flow of electric
current from the positive electrode side of the second battery
module to the negative electrode side of the first battery
module.
3. The battery unit as recited in claim 2, wherein the controller
selectively connecting and disconnecting at least one of the first
and second switches arranged in a corresponding one of the first
and second battery modules to be charged while a charging voltage
is applied to the battery unit, when a charging voltage applied
across the positive and negative electrode terminals is higher than
a voltage of the one of the first and second battery modules to be
charged and lower than a voltage across the battery modules
connected in series.
4. The battery unit as recited in claim 3, wherein the controller
includes a current sensor arranged to detect an electric current
flowing in at least one of the first and second battery modules,
the controller connecting the one of the first and second switches
when the electric current flowing in the one of the first and
second battery modules to be charged is smaller than a target
charging current, and the controller disconnecting the one of the
first and second switches when the electric current flowing in the
one of the first and second battery modules to be charged is larger
than the target charging current.
5. The battery unit as recited in claim 2, further comprising a
fourth switch operatively controlled by the controller, and the
controller selectively connecting and disconnecting the fourth
switch while a charging voltage is applied to the battery unit,
when a charging voltage applied across the positive and negative
electrode terminals is higher than a voltage of one of the first
and second battery modules to be charged and higher than a voltage
of the battery modules connected in series.
6. The battery unit as recited in claim 5, wherein the controller
includes a current sensor arranged to detect an electric current
flowing in at least one of the first and second battery modules,
the controller applying a voltage when the electric current flowing
in the one of the first and second battery modules to be charged is
smaller than a target charging current; and the controller stopping
the voltage when the electric current flowing in the one of the
first and second battery modules to be charged is larger than a
target charging current.
7. The battery unit as recited in claim 2, wherein the controller
selectively connecting and disconnecting one of the first and
second switches arranged in a corresponding one of the first and
second battery modules having a low voltage while a capacitor is
connected to the positive and negative electrode terminals.
8. A battery unit comprising: positive electrode terminal means for
connecting to an external device; negative electrode terminal means
for connecting to the external device; first electric power storing
means, connected to the positive and negative electrode terminals,
for storing electric power; first current suppressing means,
connected in series with the first electric power storing means,
for suppressing rapid current changes with respect to the first
electric power storing means; second electric power storing means,
connected in parallel with the first electric power storing means,
storing electric power; second current suppressing means, connected
in series with the second electric power storing means, for
suppressing rapid current changes with respect to the second
electric power storing means; first switch means for selectively
connecting and disconnecting a flow of electric current between the
negative electrode terminal means and a negative electrode side of
the first electric power storing means; second switch means for
selectively connecting and disconnecting a flow of electric current
between a positive electrode side of the first electric power
storing means and a positive electrode side of the second electric
power storing means; electrical bypass means for electrically
connecting a point lying between the first electric power storing
means and the first switch means to a point lying between the
second electric power storing means and the second switch means;
third switch means for selectively connecting and disconnecting a
flow of electric current in the electrical bypass means; and
controller means for controlling an on-off state of each of the
first, second and third switch means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2007-009357, filed on Jan. 18, 2007. The entire
disclosure of Japanese Patent Application No. 2007-009357 is hereby
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to a battery unit.
More specifically, the present invention relates to a battery unit
including a plurality of battery modules or blocks in which a
connection state of the battery blocks can be selectively switched
between a series connection and a parallel connection to vary the
output voltage from the battery modules or blocks.
[0004] 2. Background Information
[0005] An electric vehicle typically has a battery unit with a
plurality of battery modules electrically connected to a motor that
serves to drive the vehicle. For example, Japanese Laid-Open Patent
Publication No. 5-236608 discloses an example of a conventional
electric automobile with a motor and a vehicle electric power
supply system with a battery unit having a plurality of battery
modules or blocks electrically connected to the motor. Such a
conventional vehicle power supply system switches a connection
state of the battery unit between a state in which the battery
modules are connected in series and a state in which the battery
modules are connected in parallel. The output voltage of the
battery unit is changed by switching between the series connection
state and the parallel connection state. More specifically, in
cases where the required voltage is relatively small, the output
voltage is reduced by connecting the battery blocks in parallel.
Meanwhile, in cases where the required voltage is relatively large,
the output voltage from the battery blocks is increased by
connecting the battery blocks in series. Therefore, the efficiency
of the system is increased.
[0006] In view of the above, it will be apparent to those skilled
in the art from this disclosure that there exists a need for an
improved battery unit. This invention addresses this need in the
art as well as other needs, which will become apparent to those
skilled in the art from this disclosure.
SUMMARY OF THE INVENTION
[0007] It has been discovered that when the above described battery
is charged with an external power source, it is necessary to use a
charging apparatus having a complex structure that includes
switches, reactors, and lines for passing flywheel currents of the
reactors.
[0008] In view of this aforementioned problem of the above
described conventional technology, one object of the present
invention to provide a battery unit that does not require a complex
charging apparatus and that gradually changes the electric current
without an occurrence of a so-called surge current.
[0009] In order to achieve the above object of the present
invention, a battery unit is provided that basically comprise a
positive electrode terminal, a negative electrode terminal, a first
battery module, a second battery module, a first switch module, a
second switch module, a bypass line, a third switch module and a
controller. The first battery module is connected to the positive
and negative electrode terminals. The first battery module includes
a first battery and a first reactor connected together in series.
The second battery module is connected in parallel with the first
battery module. The second battery module includes a second battery
and a second reactor connected together in series. The first switch
module is arranged between the negative electrode terminal and a
negative electrode side of the first battery module. The second
switch module is arranged between a positive electrode side of the
first battery module and a positive electrode side of the second
battery module. The bypass line connects a point lying between the
first battery module and the first switch module to a point lying
between the second battery module and the second switch module. The
third switch module is arranged in the bypass line. The controller
is operatively arranged to control an on-off state of each of the
first, second and third switch modules.
[0010] These and other objects, features, aspects and advantages of
the present invention will become apparent to those skilled in the
art from the following detailed description, which, taken in
conjunction with the annexed drawings, discloses preferred
embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Referring now to the attached drawings which form a part of
this original disclosure:
[0012] FIG. 1 is a simplified circuit diagram of a battery unit in
accordance with one embodiment of the present invention;
[0013] FIG. 2 is a simplified circuit diagram illustrating a state
in which the battery unit is being charged while installed in a
vehicle in accordance with the illustrated embodiment;
[0014] FIG. 3A is a first control flowchart showing the control
executed by the controller for charging the first battery module
using an external electric power source;
[0015] FIG. 3B is a second control flowchart showing the control
executed by the controller for charging the second battery module
using an external electric power source;
[0016] FIG. 4 is a time chart showing the states of the charging
current and the switches when the flowcharts of FIGS. 3A and 3B are
executed;
[0017] FIG. 5A is a simplified circuit diagram illustrating the
flow of current that occurs when the charging control is executed
with respect to the first battery module;
[0018] FIG. 5B is a simplified circuit diagram illustrating the
flow of current that occurs when the charging control is executed
with respect to the first battery module;
[0019] FIG. 6A is a simplified circuit diagram illustrating the
flow of current that occurs when the charging control is executed
with respect to the second battery module;
[0020] FIG. 6B is a simplified circuit diagram illustrating the
flow of current that occurs when the charging control is executed
with respect to the second battery module;
[0021] FIG. 7A is a simplified circuit diagram showing the flow of
current that occurs when control is executed to charge both the
first and second battery modules using an external electric power
source;
[0022] FIG. 7B is a simplified circuit diagram showing the flow of
current that occurs when control is executed to charge both the
first and second battery modules using an external electric power
source;
[0023] FIG. 8A is simplified circuit diagram illustrating the flow
of current that occurs when a voltage variation correction control
in accordance with the present invention is executed in order to
correct voltage variation among the battery modules of the battery
unit;
[0024] FIG. 8B is simplified circuit diagram illustrating the flow
of current that occurs when a voltage variation correction control
in accordance with the present invention is executed in order to
correct voltage variation among the battery modules of the battery
unit; and
[0025] FIG. 9 is a simplified circuit diagram of a battery unit
having three battery modules in accordance with another embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Selected embodiments of the present invention will now be
explained with reference to the drawings. It will be apparent to
those skilled in the art from this disclosure that the following
descriptions of the embodiments of the present invention are
provided for illustration only and not for the purpose of limiting
the invention as defined by the appended claims and their
equivalents.
[0027] Referring initially to FIG. 1, a simplified circuit diagram
of a battery unit 10 is illustrated in accordance with one
embodiment of the present invention. Basically, the battery unit 10
has a first positive electrode terminal 11a, a second negative
electrode terminal 11b, an electrical line 12, a controller 15, a
first battery module 131, a second battery module 132, a first
switch module 141, a second switch module 142 and a third switch
module 143. The terminals 11a and 11b are configured and arranged
for connecting an external device thereto. The electrical line 12
electrically connects the terminals 11a and 11b via the first and
second battery modules 131 and 132 as seen in FIG. 1. In
particular, at an intermediate point of the electrical line 12, the
electrical line 12 branches into a first line 121 with the first
battery module 131 and a second line 122 with the second battery
module 132. The battery unit 10 also includes a bypass line 123
that connects a point of the first line 121 lying between the first
battery module 131 and the first switch module 141 to a point of
the second line 122 lying between the second battery module 132 and
the second switch module 142.
[0028] In the illustrated embodiment of FIG. 1, an internal
electric current of the battery unit 10 can be controlled so as to
charge the first and second battery modules 131 and 132, and the
bypass line 123 forms a flywheel circuit so that electric power
stored (the current) of a reactor can be passed through the bypass
line 123. As a result, the charging apparatus of the battery unit
10 can be simplified. Moreover, internal electric current of the
battery unit 10 gradually changes the current without surge
currents occurring.
[0029] The first battery module 131 is arranged in the first line
121. The first battery module 131 includes a battery 131a and a
reactor 131b. The battery 131a and the reactor 131b are connected
together in series. As shown in FIG. 1, an upper electrode of the
battery 131a is a positive electrode and a lower electrode is a
negative electrode. The battery 131a is, for example, a storage
battery or a capacitor storing electric power. The reactor 131b is,
for example, a coil or a capacitor having a reactor component. The
reactor 131b is configured and arranged to suppress or minimize
overcurrents that might occur.
[0030] The second battery module 132 is arranged in the second line
122. The second battery module 132 is connected in parallel with
the first battery module 131. The second battery module 132
includes a battery 132a and a reactor 132b. The battery 132a and
the reactor 132b are connected together in series. As shown in FIG.
1, an upper electrode of the battery 132a is a positive electrode
and a lower electrode is a negative electrode. The battery 132a is,
for example, a storage battery or a capacitor storing electric
power. The reactor 132b is, for example, a coil or a capacitor
having a reactor component. The reactor 132b is configured and
arranged to suppress or minimize overcurrents that might occur.
[0031] In the illustrated embodiment, for example, the first switch
module 141 is a semiconductor switch including a first diode and a
first transistor. The diode permits a flow of electric current from
a negative electrode side of the second battery module 132 to the
negative electrode side of the first battery module 131, but blocks
a flow of electric current from the negative electrode side of the
first battery module 131 to the negative electrode side of the
second battery module 132. The transistor is a current amplifying
element. In FIG. 1, the transistor is exemplified as an NPN-type
transistor. When a base current exists, a collector current flows
from the negative electrode side of the first battery module 131 to
the negative electrode side of the second battery module 132.
Hereinafter, a state in which a base current is flowing to a
transistor will be referred to as a state in which the switch is
"on".
[0032] In the illustrated embodiment, for example, the second
switch module 142 is a semiconductor switch including a second
diode and a second transistor. The second diode of the second
switch module 142 permits a flow of electric current from the
positive electrode side of the second battery module 132 to the
positive electrode side of the first battery module 131, but blocks
a flow of electric current from the positive electrode side of the
first battery module 131 to the positive electrode side of the
second battery module 132. The second transistor of the second
switch module 142 is arranged such that when a base current exists,
a collector current flows from the positive electrode side of the
first battery module 131 to the positive electrode side of the
second battery module 132.
[0033] The third switch module 143 is arranged in the bypass line
123. In the illustrated embodiment, for example, the third switch
module 143 is a third semiconductor switch including a third diode
and a third transistor. The diode of the third switch module
permits a flow of electric current from the negative electrode side
of the first battery module 131 to the positive electrode side of
the second battery module 132, but blocks a flow of electric
current from the positive electrode side of the second battery
module 132 to the negative electrode side of the first battery
module 131. The transistor of the third switch module 143 is
arranged such that when a base current exists, a collector current
flows from the positive electrode side of the second battery module
132 to the negative electrode side of the first battery module 131.
Alternatively, the third switch module 143 can be a two-way
semiconductor switch, in which case the diode is not needed.
[0034] The controller 15 controls the base currents supplied to
each of the transistors of the switch modules 141, 142 and 143, and
thereby, controls the on-off state of each of the switch modules
141, 142 and 143. The controller 15 is preferably a microcomputer
having a central processing unit (CPU), a read only memory (ROM), a
random access memory (RAM), and an input/output interface (I/O
interface). It is also acceptable for the controller 15 to be made
up of a plurality of microcomputers.
[0035] FIG. 2 is illustrates a state in which the battery unit is
being charged while installed in a vehicle. The battery unit 10 is
connected to an external electric power source 22 (a commercially
available power source or other power source) through a rectifier
21, and the battery unit 10 is charged by the external electric
power source 22. It is also acceptable for the rectifier 21 to be
provided in the battery unit 10 or in the external power source
22.
[0036] The battery unit 10 is also connected to a motor generator
32 through an inverter 31 and a circuit breaker or contactor 33.
The battery unit 10 is configured both to drive the vehicle by
supplying electric power to the motor generator 32 and to be
charged with electric power generated by the motor generator 32.
The inverter 31 includes a smoothing capacitor 31a at the input end
thereof. The circuit breaker 33 is a device that functions to
connect and disconnect an electric power supply line. Thus, the
circuit breaker 3 is configured and arranged to cut off the power
supply line. Generally, a mechanical relay or the like is used as
the circuit breaker 33.
[0037] As seen from the circuit configuration, the battery unit 10
can be switched between a state in which the first and second
battery modules 131 and 132 are connected in parallel and a state
in which the same are connected in series and can deliver or
receive electric power while in either of these connection states.
The controller 15 controls the switching of the connection state in
a known manner by controlling the switch modules 141, 142 and
143.
[0038] As a first working example of this embodiment, a charging
method (first charging method) will now be explained which is used
when the charging voltage applied to the terminals 11a and 11b from
the external power source 22 is set to be higher than the voltage
of the battery module 131 or 132 being charged and lower than the
voltage across the first and second battery modules 131 and 132
connected together in series. An example of such a case is when the
voltage of the external power source 22 is 200 V, the voltage of
the first battery module 131 is 180 V, and the voltage of the
second battery module 132 is 180 V.
[0039] FIGS. 3A and 3B are control flowcharts showing the control
executed by the controller 15 when an external power source 22 is
used to charge the battery modules 131 and 132, respectively and
the charging voltage applied to the terminals 11a and 11b from the
external power source 22 is set to be higher than the voltage of
the battery modules 131 and 132 being charged and lower than the
voltage across the first and second battery modules 131 and 132
connected together in series. The controller 15 repeatedly executes
this control processing once per prescribed amount of time (e.g.,
every 10 milliseconds).
[0040] When the external power source 22 is used to charge the
first battery module 131, the controller 15 executes the flowchart
of FIG. 3A. The voltage applied to the terminals 11a and 11b is
higher than the voltage of the first battery module 131 and lower
than the voltage across the first and second battery modules 131
and 132 connected together in series.
[0041] In step S111, the controller 15 determines if it is
necessary to charge the first battery module 131. This
determination is accomplished by determining if a target charging
current is not reached. If the target charging current is not
reached, then charging is necessary. If the target charging current
is reached, then the controller 15 determines that charging is not
necessary.
[0042] If charging is necessary, then the controller 15 proceeds to
step S112. In step S112, the controller 15 turns the first switch
module 141 on (switch-on step).
[0043] If charging is not necessary, then the controller 15
proceeds to step S113. In step S113, the controller 15 turns the
first switch module 141 off (switch-off step).
[0044] When the external power source 22 is used to charge the
second battery module 132, the controller 15 executes the flowchart
of FIG. 3 (B). The voltage applied to the terminals 11a and 11b is
higher than the voltage of the second battery module 132 and lower
than the voltage across the first and second battery modules 131
and 132 connected together in series. In step S121, the controller
15 determines if it is necessary to charge the second battery
module 132.
[0045] If charging is necessary, then the controller 15 proceeds to
step S122. In step S122, the controller 15 turns the second switch
module 142 on (switch-on step).
[0046] If charging is not necessary, then the controller 15
proceeds to step S123. In step S123, the controller 15 turns the
second switch module 142 off (switch-off step).
[0047] FIG. 4 is a time chart showing the states of the charging
current and the switches when the flowcharts of FIGS. 3A and 3B are
executed. In the following explanation, the step numbers of the
flowcharts shown in FIGS. 3A and 3B are indicated in parentheses to
illustrate the correspondence between the time chart and the
flowcharts.
[0048] At a time t0 of FIG. 4, the controller 15 determines if it
is necessary to charge the first battery module 131 (S111). As
shown in graph (A) of FIG. 4, the charging current has not reached
the target charging current and the controller 15 determines that
it is necessary to charge the first battery module 131. As shown in
graph (B) of FIG. 4, the controller 15 turns the first switch
module 141 "on" (S112: switch-on step). Then, as shown in graph (A)
of FIG. 4, the charging current flowing to the battery 131a
gradually increases. The charging current increases gradually
because the reactor 132b is connected in series with the battery
131a.
[0049] At a time t1 of FIG. 4, the charging current reaches the
target charging current (see graph (A) of FIG. 4) and the
controller 15 determines that it is not necessary to charge the
first battery module 131 (result of step S111 is No). As shown in
graph (B) of FIG. 4, the controller 15 turns the first switch
module 141 "off" (step S113: switch-off step). The charging current
then gradually decreases.
[0050] At a time t2 of FIG. 4, the charging current again falls
below the target charging current (see graph (A) of FIG. 4) and the
controller 15 determines that it is necessary to charge the first
battery module 131 (result of step S111 is Yes). As shown in graph
(B) of FIG. 4, the controller 15 turns the first switch module 141
"on" (step S113: switch-on step).
[0051] The controller 15 repeats the processing described
above.
[0052] The target charging current can be a fixed value or it can
be varied depending on the state of the battery. For example, it
can be set to a larger value when the battery module is cooled so
that the battery module can be charged more rapidly and set to a
smaller value when the battery module is heated so that the load
imposed on the battery can be lightened.
[0053] FIGS. 5A and 5B are simplified circuit diagrams illustrating
the flow of current that occurs when the charging control described
above is executed with respect to the first battery module 131.
[0054] When the first battery module 131 is charged using the
external power source 22, the external power source 22 is connected
to the terminals 11a and 11b through the rectifier 21. A voltage
VE1 that is higher than the voltage of the first battery module 131
and lower than the voltage across the first and second battery
modules 131 and 132 connected together in series is then applied to
the terminals 11a and 11b. Next, the first switch module 141 is
turned "on" (S112: switch-on step).
[0055] Since the applied voltage VE1 is higher than the voltage of
the first battery module 131 (battery 131a), the internal current
of the battery unit 10 flows through the components of the battery
unit 10 in the following order, as shown in FIG. 5A: terminal
11a.fwdarw.first battery module 131 (reactor 131b.fwdarw.battery
131a).fwdarw.first switch module 141.fwdarw.terminal
11b.fwdarw.rectifier 21. As a result, the first battery module 131
is charged. Since the first battery module 131 has a reactor 131b
connected in series with the battery 131a, the current (charging
current) passing through the first battery module 131 (battery
131a) increases gradually after the first switch module 141 is
turned "on".
[0056] When the charging current reaches the target charging
current, the first switch module 141 is turned "off" (step S113:
switch-off step). When the first switch module 141 is turned "off",
the first and second battery modules 131 and 132 are connected
together in series through the third switch module 143.
[0057] Since the applied voltage VE1 is lower than the voltage
across the first and second battery modules 131 and 132 connected
in series, the flow of current from the external power source 22 is
blocked and electric power stops being supplied to the battery unit
10. Since the first battery module 131 includes the reactor 131b,
the current flowing from the first battery module 131 (reactor
131b.fwdarw.battery 131a) through the third switch module 143 and
through the second switch module 142
(131.fwdarw.143.fwdarw.142.fwdarw. . . . ) decreases gradually as
shown in FIG. 5B.
[0058] FIGS. 6A and 6B are simplified circuit diagrams illustrating
the flow of current that occurs when the charging control described
above is executed with respect to the second battery module
132.
[0059] When the second battery module 132 is charged using the
external power source 22, the external power source 22 is connected
to the terminals 11a and 11b through the rectifier 21. Then a
voltage VE2 that is higher than the voltage of the second battery
module 132 and lower than the voltage across the first and second
battery modules 131 and 132 connected together in series is applied
to the terminals 11a and 11b. Next, the second switch module 142 is
turned "on" (S112: switch-on step).
[0060] Since the applied voltage VE2 is higher than the voltage of
the second battery module 132 (battery 132a), the internal current
of the battery unit 10 flows through the components of the battery
unit 10 in the following order, as shown in FIG. 6A: terminal
11a.fwdarw.second switch module 142.fwdarw.second battery module
132 (reactor 132b.fwdarw.battery 132a).fwdarw.terminal
11b.fwdarw.rectifier 21. As a result, the second battery module 132
is charged. Since, similarly to the first battery module 131, the
second battery module 132 has a reactor 132b connected in series
with the battery 132a, the current (charging current) passing
through the second battery module 132 (battery 132a) increases
gradually after the second switch module 142 is turned "on".
[0061] When the charging current reaches the target charging
current, the second switch module 142 is turned "off" (step S113:
switch-off step). When the second switch module 142 is turned
"off", the first and second battery modules 131 and 132 are
connected together in series through the third switch module
143.
[0062] Since the applied voltage VE2 is lower than the voltage
across the first and second battery modules 131 and 132 connected
in series, the flow of current from the external power source 22 is
blocked and electric power stops being supplied to the battery unit
10. Since the second battery module 132 includes the reactor 132b,
the current flowing from the second battery module 132 (reactor
132b.fwdarw.battery 132a) through the first switch module 141 and
through the third switch module 143
(132.fwdarw.141.fwdarw.143.fwdarw. . . . ) decreases gradually as
shown in FIG. 6B.
[0063] As explained previously, this embodiment enables a current
flowing to the first and second battery modules 131 and 132 to be
controlled by controlling the on-off states of the first and second
switch modules 141 and 142 contained inside the battery unit 10. In
this way, the first and second battery modules 131 and 132 can be
charged by controlling the internal switch modules 141 and 142.
Additionally, since the reactor 131b and 132b are connected in
series with each of the batteries 131a and 132a, respectively, the
current changes gradually instead of rapidly and surge currents are
prevented from occurring.
[0064] In this particular charging method, it is acceptable to
simply use a diode as the third switch module 143 and omit the use
of a transistor.
[0065] The explanation provided above describes a charging method
in which the first and second battery modules 131 and 132 are each
charged individually. However, if the voltage applied across the
terminals 11a and 11b from the external power source is set to be
higher than the voltage of the first battery module 131, higher
than the voltage of the second battery module 132, and lower than
the voltage across the first and second battery modules 131 and 132
connected in series, then the first and second battery modules 131
and 132 can be charged simultaneously by controlling the on-off
states of both the first switch module 141 and the second switch
module 142 at the same time so as to control the currents flowing
to the first and second battery modules 131 and 132. Since the
principle is the same, simultaneous charging is not illustrated in
the drawings. However, the flow of current during this kind of
charging will now be explained. If the first and second switch
modules 141 and 142 are both turned "on" at the same time, then the
first and second battery modules 131 and 132 will be connected in
parallel with respect to the external power source and current will
flow from the external power source to the first battery module 131
and to the second battery module 132, thereby charging the battery
modules 131 and 132. If the first and second switch modules 141 and
142 are then both turned "off" at the same time, then the first and
second battery modules 131 and 132 will be connected in series with
respect to the external power source and current from the external
power source will be blocked, thereby causing charting of the
battery modules 131 and 132 to stop.
[0066] This embodiment is also applicable when the battery is
discharged. By controlling the on-off state of the third switch
module 143 in accordance with the discharge current flowing to the
reactors 131b and 132b, the voltage at the input terminals of the
inverter 31 can be controlled to any desired voltage.
[0067] In conventional battery unit systems, the circuitry for
switching the connection state of the battery modules between
series and parallel has required fuses and/or reactors to be
provided between the battery modules and the inverter in order to
suppress abnormal currents (surge currents) occurring due to the
potential differences between the inverter and the battery modules
being connected during the switch from series to parallel or
parallel to series. Additionally, in order to charge the battery
unit with an external power source, it has been necessary to have a
separate charging apparatus that comprises a plurality of switches
and reactors.
[0068] With the illustrated embodiment, as explained previously,
the first and second battery modules 131 and 132 are provided with
the reactors 131b and 132b, respectively, which are connected in
series with the batteries 131a and 132a such that abnormal currents
can be suppressed and voltages can be adjusted. Thus, by
controlling the on-off states of the first and second switch
modules 141 and 142 provided inside the battery unit 10, the
current flowing to the first and second battery modules 131 and 132
can be controlled so as to charge the first and second battery
modules 131 and 132. Consequently, it is not necessary to use a
charging apparatus comprising switches and reactors. Additionally,
since a reactor 131b and 132b is connected in series with each of
the batteries 131a and 132a, the current changes gradually instead
of rapidly and surge currents are prevented from occurring.
[0069] FIGS. 7A and 7B are simplified circuit diagrams illustrating
the flow of current that occurs when the charging control is
executed with respect to the first and second battery modules 131
and 132 using the external power source 22 while the voltage
applied to the terminals 11a and 11b from the external power source
22 is set to a voltage that is higher than the voltage across the
first and second battery modules 131 and 132 connected together in
series. An example of such a case is when the voltage of the
external power source 22 is 300 V, the voltage of the first battery
module 131 is 140 V, and the voltage of the second battery module
132 is 140 V.
[0070] In this case, the battery unit 10 is connected to the
external power source 22 through a charging switch 201 and a
rectifier 21 and the battery unit 10 is charged using the external
power source 22. The charging switch 201 constitutes a fourth
switch module that is controlled by the controller 15.
[0071] When the first and second battery modules 131 and 132 are
charged using the external power source 22, the external power
source 22 is connected to the terminals 11a and 11b through the
charging switch 201 and the rectifier 21. A voltage VE3 that is
higher than the voltage across the first and second battery modules
131 and 132 connected together in series is then applied to the
terminals 11a and 11b. Next, the charging switch 201 is turned "on"
(voltage applying step).
[0072] Since the applied voltage VE3 is higher than the voltage
across the first battery unit 131 and the second battery unit 132
connected together in series (i.e., higher than the series voltage
of the battery 131a and the battery 132a), the internal current of
the battery unit 10 flows through the components of the battery
unit 10 in the following order, as shown in FIG. 7A: terminal
11a.fwdarw.first battery module 131 (reactor 131b.fwdarw.battery
131a).fwdarw.third switch module 143.fwdarw.second battery module
132 (reactor 132b.fwdarw.battery 132a).fwdarw.terminal
11b.fwdarw.rectifier 21. As a result, the first and second battery
modules 131 and 132 are charged. Additionally, since each of the
battery modules 131 and 132 has a reactor connected in series with
the battery, the current (charging current) passing through the
battery modules (batteries) increases gradually after the charging
switch 201 is turned "on".
[0073] When the target charging current is reached, the charging
switch 201 is turned "off" and the voltage application from the
external power source 22 stops (voltage application stopping step).
When the charging switch 201 is turned "off", the internal currents
of the battery unit 10 gradually decrease while flowing through the
components of the battery unit 10 in the following orders, as shown
in FIG. 7B: first battery module 131 (reactor 131b.fwdarw.battery
131a).fwdarw.third switch module 143.fwdarw.second switch module
142, and second battery module 132 (reactor 132b.fwdarw.battery
132a).fwdarw.first switch unit 141.fwdarw.third switch module
143.
[0074] As explained previously, by controlling the on-off state of
the charging switch 201 that controls whether or not the voltage is
applied to the battery unit 10, the current flowing to the first
and second battery modules 131 and 132 can be controlled such that
the first and second battery modules 131 and 132 are charged
simultaneously. Additionally, since a reactor 131b and 132b is
connected in series with each of the batteries 131a and 132a, the
current changes gradually instead of rapidly and surge currents are
prevented from occurring.
[0075] In this particular charging method, it is acceptable to
simply use a diode for each of the first switch module 141, the
second switch module 142, and the third switch module 143 and omit
the use of a transistor.
[0076] FIGS. 8A and 8B are simplified circuit diagrams illustrating
the flow of current that occurs when a voltage variation correction
control in accordance with the present invention is executed in
order to correct voltage variation among the battery modules of the
battery unit 10.
[0077] Even if the first and second battery modules 131 and 132 are
made to the same specifications, the characteristics thereof can
differ slightly due to manufacturing variations and the difference
in the characteristics can cause variation to exist in the voltages
of the battery modules. A control serving to correct this kind of
voltage variation will now be explained.
[0078] When the voltage of the first battery module 131 is higher
than the voltage of the second battery module 132, the contactor 33
is first turned "on" and the capacitor 31a is connected to the
terminals 11a and 11b. Then, the second switch module 142 is turned
"on" (switch-on step). After the second switch module 142 is turned
"on", a current flows through the internal components of the
battery unit 10 in the following order, as shown in FIG. 8A: first
battery module 131 (battery 131a.fwdarw.reactor 131b).fwdarw.second
switch module 142.fwdarw.second battery module 132 (reactor
132b.fwdarw.battery 132a).fwdarw.first switch module 141.
Additionally, since each of the battery modules 131 and 132 has a
reactor connected in series with the battery, the current (charging
current) passing through the battery modules (batteries) increases
gradually after the second switch module 142 is turned "on".
[0079] Next, the second switch module 142 is turned "off"
(switch-off step) and, as shown in FIG. 8B, the current exiting the
first battery module 131 (battery 131a.fwdarw.reactor 131b) flows
as follows: terminal 11a.fwdarw.contactor 33.fwdarw.inverter
31.fwdarw.(capacitor 31a).fwdarw.terminal 11b.fwdarw.first switch
module 141.fwdarw.first battery module 131. Meanwhile, the current
exiting the second battery module 132 (reactor 132b.fwdarw.battery
132a) flows as follows: first switch module 141.fwdarw.third switch
module 143.fwdarw.second battery module 132.
[0080] Next, the second switch module 142 is turned "on" again
(switch-on step) and the current flows as shown in FIG. 8A. By
turning the second switch module 142 on and off in this fashion,
electric charge can be transferred from the first battery module
131 (whose electric potential is higher) to the second battery
module 132 (whose electric potential is lower) and the state of the
voltage of the first battery module 131 being higher than the
voltage of the second battery module 132 can be corrected.
[0081] When the voltage of the second battery module 132 is higher
than the voltage of the first battery module 131, the voltage
difference can be corrected in a similar manner by controlling the
on-off state of the first switch module 141. Thus, voltage
variation between the battery modules of the battery unit 10 can be
corrected by merely controlling the on-off states of the first
switch module 141 or the second switch module 142 contained inside
the battery unit 10.
[0082] The battery module voltage variation correction control
described above can also be executed when the inverter 31 and the
motor generator 32 are being controlled for the generation of
electricity. The voltage variation (difference) between the first
and second battery modules 131 and 132 can be corrected by
controlling the on-off state of the first switch module 141 or the
second switch module 142 in accordance with the size relationship
between the voltages of the battery modules 131 and 132.
[0083] Referring now to FIG. 9, a battery unit 110 in accordance
with a second embodiment will now be explained. In view of the
similarity between the first and second embodiments, the parts of
the second embodiment that are identical to the parts of the first
embodiment will be given the same reference numerals as the parts
of the first embodiment. Moreover, the descriptions of the parts of
the second embodiment that are identical to the parts of the first
embodiment may be omitted for the sake of brevity.
[0084] The first embodiment illustrates an example in which the
battery unit 10 has two battery modules in order to make the main
aspects of the invention easier to understand. However, a similar
control can be accomplished with respect to the battery unit 110
having three battery modules as shown in FIG. 9. More specifically,
in a situation where the first switch module 141 would be
controlled if the battery unit 10 had two battery modules, the
first switch modules 141a and 141b of the battery unit 110 with
three battery modules is similarly controlled. Similarly, in a
situation where the second switch module 142 would be controlled if
the battery unit had two battery modules, the second switch modules
142a and 142b of the battery unit 110 with three battery modules is
similarly controlled. In a situation where the third switch module
143 would be controlled if the battery unit had two battery
modules, the third switch modules 143a and 143b of the battery unit
having three battery modules is similarly controlled. In this way,
the battery unit 110 with three battery modules (as shown in FIG.
9) can be controlled in a similar manner to a battery unit having
two battery modules. Expanding on this idea, a similar control can
be accomplished with respect to a battery unit having four or more
battery modules.
General Interpretation of Terms
[0085] In understanding the scope of the present invention, the
term "comprising" and its derivatives, as used herein, are intended
to be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including", "having" and their derivatives. Also, the terms
"part," "section," "portion," "member" or "element" when used in
the singular can have the dual meaning of a single part or a
plurality of parts.
[0086] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the invention as defined in the appended claims. For example,
the size, shape, location or orientation of the various components
can be changed as needed and/or desired. Components that are shown
directly connected or contacting each other can have intermediate
structures disposed between them. The functions of one element can
be performed by two, and vice versa. The structures and functions
of one embodiment can be adopted in another embodiment. It is not
necessary for all advantages to be present in a particular
embodiment at the same time. Every feature which is unique from the
prior art, alone or in combination with other features, also should
be considered a separate description of further inventions by the
applicant, including the structural and/or functional concepts
embodied by such feature(s). Thus, the foregoing descriptions of
the embodiments according to the present invention are provided for
illustration only, and not for the purpose of limiting the
invention as defined by the appended claims and their
equivalents.
* * * * *